Dynamic Brillouin gratings permanently sustained by chaotic lasers.

A method to induce only one permanent and localized dynamic Brillouin grating in polarization maintaining optical fibers is introduced. The generation of the grating exploits the thumbtack correlation of the chaotic laser signals. A numerical calculation, corroborated by a theoretical analysis, is performed and the grating properties, length, and reflectance determined.

[Definition of neurotoxic risk based on the benchmark dose in vitro: illustration with experimental models based on the use of known neurotoxic substances]. / Definizione del rischio neurotossico in base alla dose di riferimento ("benchmark dose") in vitro: esemplificazioni con modelli sperimentali basati sull'uso di sostanze neurotossiche note.

The BMD approach has been used to compare the cell viability (MTT assay) of different rat (C6 and PC12, glial and neuronal, respectively) and human cell lines (D384 and SK-N-MC, glial and neuronal, respectively) after 24-h exposure to the following neurotoxic substances: Manganese Chloride (MnCl2), Methyl-mercury (Me-Hg) and the enantiomers of Styrene Oxide (SO). For all rat and human cell lines, the potency of the examined compounds was: MnCl2 < S-SO < R-SO < Me-Hg. A preliminary comparison with in vivo toxicity data for these substances gave rise to consistent results. Whereas a reasonable agreement between in vitro and in vivo data has been found for Mn and styrene oxide, a wide scatter of LOAEL has been reported for Me-Hg and these appear to be either much higher or lower than the BMD for the MTT assay we observed in vitro.